ON ATAVISTIC VARIATION IN OENOTHERA CRUCIATA. 337 



Afterwards 1 continued these four strains, sowing from the two 

 last named in 1900, from the first named in 1901. The atavistic 

 mothers gave only children which were in this regard like them. 

 The purely cruciate strains on the other hand continued to produce 

 atavistic and intermediate types, and these last were also inconstant 

 as far as 1 observed them. 



Taking the five generations together, 1 had 232 children from 

 cruciate mothers, 103 from intermediate and 141 from atavistic 

 parents. The first group consisted of 85 per cent, cruciate, 5 per 

 cent, intermediate and 10 per cent, atavistic individuals. The 

 second, of 4 per cent, cruciate, no intermediate and 96 per cent, 

 atavistic specimens. The third was nearly constant, all individuals 

 bearing the broad obcordate petals. 



I say nearly constant, for among those atavists I observed some 

 cases of bud-variation, by which they returned to the cruciate 

 type. This rare phenomenon occasionally presents itself without 

 apparent reason, but it may be induced to appear oftener in the 

 following manner. Around the main stem the plants produce a 

 circle of smaller stems growing upwards from the axils of the root 

 leaves. In my cultures these side-stems do not ordinarily become 

 tall enough to bear flowers. But by cutting out the main stem at 

 an early period I could induce the others to a more vigorous growth. 

 1 repeatedly made this experiment, but will only cite here obser- 

 vations made on a single plant in the summer of 1901, grown from 

 seed of a purely cruciate parent. It made six side-stems, out of 

 which three bore only atavistic or broad-petalled flowers. The 

 three other stems likewise produced obcordate petals, but not 

 exclusively, bearing on one side of the spike flowers with the 

 narrow and variable petals of the above-named intermediate 

 types. 



Such cases prove that the atavistic individuals are not, or at 

 least are not always, so constant as could be deduced from the 

 figures above given. Analogous instances of sectorial variation, 

 one sector of the spike bearing other flowers than the remaining 

 sectors, were from time to time observed on atavistic individuals 

 and also on intermediate ones, the sport giving flowers with ob- 

 cordate petals. As yet I have found no such sports on plants of the 

 purely cruciate type nor purely cruciate flowers on those of the two 

 other types. But I have no doubt that this is only due to the small 

 extent of my cultures. 



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